disallow GOTO when it could corrupt the estack

- this occurs inside a FOR or CASE statement
- GOTO out of a WHILE or REPEAT loop  works

tests/gototest.pas

@@ -0,0 +1,22 @@
+program gototest;
+var i:integer;
+label l1,l2;
+begin
+	goto l1;
+	writeln('skipped');
+	l1: writeln('goto destination 1');
+	{
+	for i := 1 to 10 do
+	begin
+		goto l2;
+	end;
+	}
+	{
+	case i of
+	1: writeln('1');
+	2: goto l2;
+	3..10: writeln('3 - 10');
+	end;
+	l2: writeln('goto destination 2');
+	}
+end.